1. Field of Invention
This invention relates to toners, a method of making the toners, developers containing the toners, a method of making coated carriers for the developers, and a method of forming images of offset-like print quality with the developers. More in particular, the invention relates to toners and developers having carefully controlled properties to that provide offset-like print quality when used in developing electrostatic images with a device containing a hybrid scavengeless development system.
2. Description of Related Art
Historically, xerography has not been required to deliver prints of the same caliber as offset lithography. The offset lithography customer demands a level of print quality much higher than is available from conventional xerographic machines.
U.S. Pat. No. 5,545,501 describes an electrostatographic developer composition comprising carrier particles and toner particles with a toner particle size distribution having a volume average particle size (T) such that 4 .mu.m.ltoreq.T.ltoreq.12 .mu.m and an average charge (absolute value) pro diameter in femtocoulomb/10 .mu.m (C.sub.T) after triboelectric contact with said carrier particles such that 1 fC/10 .mu.m.ltoreq.C.sub.T.ltoreq.10 fC/10 .mu.m characterized in that (i) said carrier particles have a saturation magnetization value, M.sub.sat, expressed in Tesla (T) such that M.sub.sat.gtoreq.0.30 T, (ii) said carrier particles have a volume average particle size (C.sub.avg) such that 30 .mu.m.ltoreq.C.sub.avg.ltoreq.60 .mu.m, (iii) said volume based particle size distribution of said carrier particles has at least 90% of the particles having a particle diameter C such that 0.5 C.sub.avg.ltoreq.C.ltoreq.2 C.sub.avg, (iv) said volume based particles size distribution of said carrier particles comprises less than b % particles smaller than 25 .mu.m wherein b=0.35 X (M.sub.sat).sup.2 X P with M.sub.sat : saturation magnetization value, M.sub.sat, expressed in T and P: the maximal field strength of the magnetic developing pole expressed in kA/m, and (v) said carrier particles comprise a core particle coated with a resin coating in an amount (RC) such that 0.2% w/w.ltoreq.RC.ltoreq.2% w/w. See the Abstract. This patent describes that such developer achieves images of offset-quality in systems in which a latent image is developed with a fine hair magnetic brush. See column 4, lines 7-17.
What is still desired is a set of developers comprised of toners and carriers that possess a combination of properties such that when used to develop a latent image on the surface of a photoreceptor, preferably in an image-on-image device, more preferably in a device utilizing a hybrid scavengeless development system, the color image produced in this xerographic manner exhibits a quality analogous to that achieved in offset lithography.